小编use*_*604的帖子

我想绘制以下场方程:

• dx/dt = x*(4*y + 3*x-3)
• dy/dt = y*(4*y + 3*x-4)

但我不知道如何将边界限制为三角形x>=0, y>=0, x<=1-y:

# stream plot with matplotlib
import numpy as np
import matplotlib.pyplot as plt
def velocity_i(x,y):
    vx = x*(3*x+4*y-3)
    vy = y*(3*x+4*y-4)
    return vx, vy
n=100
x = np.linspace(0, 1, n)
y = np.linspace(0, 1, n)
X, Y = np.meshgrid(x, y)
Ux, Uy = velocity_i(X, Y)
vels = (Ux**2+Uy**2)**0.5
plt.figure(figsize=(5,4))
stream = plt.streamplot(X, Y,
              Ux,Uy,
              arrowsize=1,
              arrowstyle='->',
              color= vels,
              density=1,
              linewidth=1,
                       )
plt.xlabel(r"$\Omega_{\rm m}$",fontsize='14')
plt.ylabel(r"$\Omega_{\rm …